The 20-year-old Wales prop, who joined the Bulls on a season-long loan from Warrington, has undergone surgery to remove a piece of bone from the top of his femur.
Evans also had a tear to his hip cartilage repaired and the procedure has been hailed as a success, although he will be sidelined for the next 16 weeks.
Coach Francis Cummins is now hoping to bring in a short-term replacement.
"It's disappointing for Ben and for the club because we had high hopes for him this season," said Cummins.
"However, it's a problem that needed putting right and he had quite a big operation. The good news is that it went really well and we have to rehab him now.
"Hopefully in a few months' time we'll get Ben back, but in the meantime we may have to look at bringing in players on month-to-month loan deals."
- Sports & Recreation